1. Field
Embodiments relate to a method for forming a PN junction in graphene through the application of DNA and a PN junction structure formed thereby. More particularly, embodiments relate to formation of an organic material-based semiconductor junction structure by coating a nucleotide sequence-controllable DNA molecule on a graphene surface.
2. Description of the Related Art
A PN junction refers to a boundary or an interface between two regions exhibiting a p-type property and an n-type property inside a semiconductor. The PN junction is a key structure of many semiconductor devices because it can perform lots of important functions. In case an electric current flows in a forward direction, injection of minority carriers from each region to the opposite region occurs, and this is used in an emitter of a junction transistor or a light-emitting diode, a junction laser, and the like. When voltage is applied in a reverse direction, phenomena such a minority carrier collection, electrostatic capacity characteristics of a depletion layer, and an electron avalanche multiplication in a depletion layer are produced. These phenomena are used in a collector and a condenser of a junction transistor, an avalanche photo diode, and the like.
Graphene is a material having a two-dimensional (2D) structure of carbon atoms arranged in a honeycomb lattice, and is made of a one atom-thick flat layer of carbon. Graphene is prone to build a 2D structure due to a specific atomic arrangement structure. Further, electrons behave like massless “Dirac” particles in graphene because electrons can penetrate into graphene at a high speed due to a very high charge mobility with a rest mass close to zero in the vicinity of carbon atoms. Thus, graphene has a high applicability as a sensor and a semiconductor circuit device, is advantageous in constructing a semiconductor device due to a small reduction in resistance caused by scattering, and provides advantages of process and manufacturing easiness.
However, contrary to silicon which is a semiconductor, graphene has no gap between a valence band and a conduction band. A band gap is an essential property for enabling a material used in manufacturing a transistor to allow turning on and off of an electric current. One method of introducing a band gap into graphene is to dope graphene, but in this instance, doping should be carefully performed without degrading the electrical properties inherent to graphene.
Typically, doping of graphene is performed through a chemical method. For localized doping, a diffusion process and an ion implantation process are usually applied. However, graphene doping by a diffusion process precludes localized doping in only a desired region, and thus, becomes an obstacle to integration of devices. Also, a graphene surface doping process by an ion implantation technique generates a lattice defect in graphene by ion collision, which reduces electron mobility of graphene. Further, these processes have disadvantages in that they require a high temperature process and high energy consumption to diffuse impurities by a concentration difference and to cause ions accelerated by the electric field to produce a lattice defect, need long time in a doping process, and have a probability of loss of electrical properties due to damage to an atomic arrangement structure of graphene during a process.